1. Field of the Invention
The present invention relates generally to methods and materials for fabricating thin film resistors employed within microelectronics fabrications. More particularly, the present invention relates to methods and materials for efficiently and economically fabricating thin film resistors employed within thin film resistor components, such as but not limited to thin film resistor chips, within microelectronics fabrications, such as but not limited to hybrid circuit microelectronics fabrications.
2. Description of the Related Art
Common in the art of microelectronics fabrication is the use of thin film resistors as passive electrical circuit elements and/or load bearing electrical circuit elements within electrical circuits. Thin film resistors may be employed within electrical circuits within microelectronics fabrications including but not limited to integrated circuit microelectronics fabrications and hybrid circuit microelectronics fabrications.
When employed within integrated circuit microelectronics fabrications, thin film resistors are typically formed through photolithographic patterning, through methods as are conventional in the art, of blanket layers of thin film resistor materials formed upon insulator layers which in turn are formed over semiconductor substrates, portions of which semiconductor substrates are subsequently parted to form integrated circuit chips. Similarly, when employed within hybrid circuit microelectronics fabrications, thin film resistors are typically formed through photolithographic patterning, through methods as are conventional in the art, of blanket layers of thin film resistor materials which are formed upon insulator substrates, such as but not limited to glass insulator substrates and ceramic insulator substrates, portions of which insulator substrates are subsequently parted to form discrete thin film resistor chips.
When forming thin film resistors employed in either integrated circuit microelectronics fabrications or hybrid circuit microelectronics fabrications it is common in the pertinent art, after having formed a photolithographically patterned layer of a thin film resistor material, to trim with a focused laser beam portions of the photolithographically patterned layer of the thin film resistor material to form a trimmed patterned photolitliographically patterned layer of the thin film resistor material from which is subsequently formed an integrated thin film resistor within an integrated circuit chip or a discrete thin film resistor within a discrete thin film resistor chip. Through the laser trimming method there is provided an integrated thin film resistor or a discrete thin film resistor having a precise and controlled resistance.
While the use of photolithographic patterning methods in conjunction with laser trimming methods for forming discrete thin film resistors upon insulator substrates which are subsequently parted in forming discrete thin film resistor chips for use within hybrid circuit microelectronics fabrications has thus become quite common in the art of hybrid circuit microelectronics fabrication, the use of photolithographic methods in conjunction with laser trimming methods for forming discrete thin film resistors upon insulator substrates which are subsequently parted in forming discrete thin film resistor chips for use within hybrid circuit microelectronics fabrications is not entirely without problems. In particular, in comparison with the art of integrated circuit fabrication, where several patterned layers or patterned regions within an integrated circuit in addition to a patterned thin film resistor layer within the integrated circuit are typically formed through photolithographic methods, when forming a discrete thin film resistor chip to be employed within a hybrid circuit microelectronics fabrication it is common that the only patterned layers to be formed through photolithographic methods are: (1) a patterned thin film resistor layer; and (2) a pair of patterned conductor lead layers formed contacting the patterned thin film resistor layer. Thus, within discrete thin film resistor chip fabrication, photolithographic apparatus and materials are typically generally inefficiently employed when forming discrete thin film resistor chips, thus ultimately adding additional fabrication costs to discrete thin film resistor chips.
As an additional consequence of employing photolithographic methods in forming patterned thin film resistor layers and patterned conductor lead layers upon insulator substrates portions of which are subsequently parted in forming discrete thin film resistor chips, there is also typically required insulator substrates of enhanced surface flatness and finish in order to provide for adequate registration of those insulator substrates within conventional photolithographic apparatus which are employed in forming patterned thin film resistor layers and patterned conductor lead layers contacting those patterned thin film resistor layers. Insulator substrates of enhanced flatness and finish also add fabrication cost to discrete thin film resistor chips formed through such conventional photolithographic methods and apparatus.
It is thus towards the goal of providing a method for forming discrete thin film resistors for use within discrete thin film resistor chips employed within hybrid circuit microelectronics fabrications, while: (1) avoiding discrete thin film resistor fabrication costs associated with photolithographic methods, materials and apparatus conventionally employed in forming discrete thin film resistors; and (2) avoiding discrete thin film resistor fabrication costs associated with insulator substrates of enhanced flatness and surface finish conventionally employed in forming discrete thin film resistors for use within discrete thin film resistor chips, that the present invention is directed.
Various disclosures pertaining to thin film resistor design and fabrication may be found in the art. Most commonly, the disclosures are directed towards thin film resistor materials and methods for fabrication of thin film resistors employing the thin film resistor materials, where the thin film resistors so formed exhibit improved or controlled thin film resistor properties, such as but not limited to sheet resistance, thermal coefficient of resistivity (TCR) and thermal stability. See, for example: (1) Yamazaki et al. in U.S. Pat. No. 4, 042,479 (improved thin film resistors formed from tantalum-aluminum nitride thin film resistor materials); (2) Yasujima et al. in U.S. Pat. No. 4,063,211 (improved thin film resistors formed from tantalum silicide thin film resistor materials); (3) Yasujima et al. in U.S. Pat. No. 4,338,145 (improved thin film resistors formed from tantalum-chromium alloy thin film resistor materials); (4) Paulson et al. in U.S. Pat. No. 4,510,178 (improved thin film resistors formed from chromium silicide/nitride thin film resistor materials); (5) Hall, in U.S. Pat. No. 5,023,589 (improved thin film resistors formed from gold doped nickel-chromium alloy thin film resistor materials); and (6) Krause et al., in U.S. Pat. No. 4,987,010 (improved thin film resistors formed from plasma enhanced chemical vapor deposited (PECVD) insulator layer overcoated platinum thin film resistor materials).
Desirable in the art are additional methods and materials through which there may be formed discrete thin film resistors for use within discrete thin film resistor chips employed within hybrid circuit microelectronic fabrications, where the discrete thin film resistors may be formed: (1) while avoiding use of photolithographic methods, materials and apparatus in forming the discrete thin film resistors; and (2) while avoiding use of highly polished substrates in forming the discrete thin film resistors. It is towards the foregoing goals that the present invention is specifically directed.